MySQL系列--2.常用的命令
2019-04-10 22:13
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1 、创建数据库
#语法: CREATE DATABASE dbName; #创建数据库rms create database rms;
2、切换数据库
#选择数据库 USE dbName; #选择数据库rms; use rms;
3、 查看所有的数据库名称
SHOW DATABASES;
4、创建表
#语法: #columnName:字段名称 #columnType:字段类型 CREATE TABLE tableName(columnName,columnTypei); #创建表customers CREATE TABLE `customers` ( `customerNumber` int(11) NOT NULL, `customerName` varchar(50) NOT NULL, `contactLastName` varchar(50) NOT NULL, `contactFirstName` varchar(50) NOT NULL, `phone` varchar(50) NOT NULL ) ;
5、查看数据库中所有的表
SHOW TABLES;
6、查看表结构
#语法: DESC tableName; #查看customes的结构 DESC customers; mysql> DESC customers; +------------------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +------------------+-------------+------+-----+---------+-------+ | customerNumber | int(11) | NO | | NULL | | | customerName | varchar(50) | NO | | NULL | | | contactLastName | varchar(50) | NO | | NULL | | | contactFirstName | varchar(50) | NO | | NULL | | | phone | varchar(50) | NO | | NULL | | +------------------+-------------+------+-----+---------+-------+ 5 rows in set (0.03 sec)
7、插入数据
#语法: INSERT INTO tableName(columnName1,columnName2,columnName N)values(value1,value2,valueN); #columeName也可以不写 INSERT INTO tableName values(value1,value2,valueN); INSERT INTO customers(customerNumber,customerName,contactLastName,contactFirstName,phone)values(001,"Stephen Wang",'Stephen','Wang','15687965432'); INSERT INTO customers(customerNumber,customerName,contactLastName,contactFirstName,phone)values(003,"Lucy Liu",'Lucy','Liu','15687965432');
8、查看表中的数据
#语法: SELECT * FROM tableName; mysql> select * from customers; +----------------+--------------+-----------------+------------------+-------------+ | customerNumber | customerName | contactLastName | contactFirstName | phone | +----------------+--------------+-----------------+------------------+-------------+ | 2 | Vicent Wang | Vicent | Wang | 15687965438 | | 1 | Stephen Wang | Stephen | Wang | 15687965432 | | 3 | Lucy Liu | Lucy | Liu | 15687965432 | +----------------+--------------+-----------------+------------------+-------------+ 3 rows in set (0.00 sec) #查看表中的某些字段,语法: SELECT columnName1,columnName2 from tableName; mysql> select customerNumber,customerName from customers; +----------------+--------------+ | customerNumber | customerName | +----------------+--------------+ | 2 | Vicent Wang | | 1 | Stephen Wang | | 3 | Lucy Liu | +----------------+--------------+ 3 rows in set (0.00 sec) #where条件 #查看客户编号为1的记录 mysql> select customerNumber,customerName from customers where customerNumber=1; +----------------+--------------+ | customerNumber | customerName | +----------------+--------------+ | 1 | Stephen Wang | +----------------+--------------+ 1 row in set (0.00 sec)
9、 更新数据
#语法: UPDATE tableName SET columeName=value where conditions; #将客户编号为1的客户手机号修改为15997654325 mysql> update customers set phone='15997654325' where customerNumber=1; Query OK, 1 row affected (0.62 sec) Rows matched: 1 Changed: 1 Warnings: 0
10、模糊查询
#语法: select * from tableName where columnName like ''condition [and /or] [columeName = value]; #查询表里last name为Wang的客户 mysql> select * from customers where contactFirstName like '%wang'; +----------------+--------------+-----------------+------------------+-------------+ | customerNumber | customerName | contactLastName | contactFirstName | phone | +----------------+--------------+-----------------+------------------+-------------+ | 2 | Vicent Wang | Vicent | Wang | 15687965438 | | 1 | Stephen Wang | Stephen | Wang | 15997654325 | +----------------+--------------+-----------------+------------------+-------------+ 2 rows in set (0.08 sec)
11、排序与分组
排序语法: select * from tableName order by columnName asc / desc; #按照客户编号递增排序 mysql> select * from customers order by customerNumber asc; +----------------+--------------+-----------------+------------------+-------------+ | customerNumber | customerName | contactLastName | contactFirstName | phone | +----------------+--------------+-----------------+------------------+-------------+ | 1 | Stephen Wang | Stephen | Wang | 15997654325 | | 2 | Vicent Wang | Vicent | Wang | 15687965438 | | 3 | Lucy Liu | Lucy | Liu | 15687965432 | +----------------+--------------+-----------------+------------------+-------------+ 3 rows in set (0.00 sec) #分组语法 #按照contactFirstName分组并统计客户个数 mysql> select contactFirstName,count(*) from customers group by contactFirstName; +------------------+----------+ | contactFirstName | count(*) | +------------------+----------+ | Liu | 1 | | Wang | 2 | +------------------+----------+ 2 rows in set (0.03 sec)
12、修改字段名称
#新增字段语法: alter table tableName add columnName; #修改字段语法: alter table tableName modify columnName; #删除字段语法: alter table tableName drop columnName; #customers添加一个状态字段,类型为char(20) mysql> alter table customers add staus char(20); Query OK, 0 rows affected (0.78 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> select * from customers; +----------------+--------------+-----------------+------------------+-------------+-------+ | customerNumber | customerName | contactLastName | contactFirstName | phone | staus | +----------------+--------------+-----------------+------------------+-------------+-------+ | 2 | Vicent Wang | Vicent | Wang | 15687965438 | NULL | | 1 | Stephen Wang | Stephen | Wang | 15997654325 | NULL | | 3 | Lucy Liu | Lucy | Liu | 15687965432 | NULL | +----------------+--------------+-----------------+------------------+-------------+-------+ 3 rows in set (0.00 sec)
13.、删除
#删除表中的记录,语法: delete from tableName where conditions; mysql> delete from customers where customerNumber=1; Query OK, 1 row affected (0.06 sec #删除表数据和结构,语法: drop table tableName; mysql> drop table customers; Query OK, 0 rows affected (0.16 sec) #删除数据库,语法: drop database dbName; mysql> drop database rms; Query OK, 0 rows affected (0.13 sec)
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